The invention relates to a conveyor chain for a gripper system-bearing chain conveyor of a printing press, the conveyor chain having standard chain links and special chain links, both types of which are formed by link pins carrying chain rollers, and chain plates articulatedly connecting the link pins to one another, the special chain links serving to connect the conveyor chain to the gripper system, and relates as well to a sheet-processing printing press with a chain conveyor having gripper bars for transporting sheets, the gripper bars being borne by revolving conveyor chains when operating.
During practical usage of a conveyor chain of the aforementioned type in a chain conveyor of a printing press, wherein the chain conveyor bears a gripper system, the conveyor chain, when operating, passes through a closed chain path having at least two turning regions. In this regard, at least one of the turning regions is realized by a sprocket which meshes with the conveyor chain and drives the latter.
The gripper system is formed by gripper bars bearing sheet grippers. These bars extend in the longitudinal direction of the gripper system, transversely to the aforementioned chain path. At first ends of the gripper bars, the latter are connected to a first conveyor chain of the type mentioned at the introduction hereto, and at second ends of the gripper bars, the latter are connected to a second conveyor chain of the type mentioned at the introduction hereto. The chain rollers are guided by inner and outer chain guides, of which, depending upon the requirements as to the stability of the chain guides, the inner ones are interrupted within part of the turning region formed by the sprocket, or have a contour which runs within the root circle of the sprocket. These inner chain guides have end sections which run laterally of the sprocket and along which the chain rollers are gradually brought by the chain guides up to the root circle of the sprocket and lifted out of the latter, respectively. The end sections have a guide surface for the chain rollers which is narrowed at least by the extent of thickness of the sprocket teeth.
Chain conveyors constructed in this manner have become known heretofore, for example, from the printing presses marketed under the model designation SM102 by Heidelberg Druckmaschinen A. G., the German corporate assignee of the instant application. The chain conveyors serve herein for accepting a respective sheet from an impression cylinder and further transporting the sheet to a pile station, the conveyor chain being prevented, in particular, from entering the toothing of the sprocket with a jolt, by configuring the course of the end sections of the inner chain guides so that a respective chain roller entering a tooth gap in the sprocket reaches the root circle of the latter only after tracing a relatively large angle of rotation of the sprocket, and is subsequently lifted by the narrowed guide surface of the end sections.
The advantage that the conveyor chain is infed for the most part free of jolting into the toothing of the sprocket, due to the described configuration of the end sections of the inner chain guides, is disadvantageously opposed, however, by the fact that, in particular, the aforementioned end sections are responsible for wearing of the chain conveyor, which is based on the fact that, along a specific travel path of these end sections, the guide surface thereof extends concentrically with the root circle of the sprocket and has the curvature of the latter. Along this travel path, it is thus possible for the chain rollers, on the one hand, to contact the guide surface while, on the other hand, the engagement in the toothing of the sprocket counteracts any rolling of the chain rollers on the guide surface.
In a largely load-free state, the thereat occurring frictional conditions would be relatively nonproblematic. However, forces act upon the chain rollers, above all on those special chain links which bear the gripper bars, and these forces considerably increase the frictional forces by comparison with those on the chain links which are largely load-free. These forces act in an intensified manner, and in a particularly wear-promoting manner, within the aforementioned travel path of the end sections of the chain guides, because this travel path is located in the turning region of the sprocket. Thereat, at the high processing speeds of modern printing presses, which process large-format sheets and for this purpose have gripper bars of relatively great weight, considerable centrifugal forces prevail and, depending upon the position of the center of gravity on the gripper bars, exert upon the special chain links considerable tilting moments, which are reinforced via the chain rollers of the special chain links on the inner and outer chain guides.
If, for example, the further aforementioned transfer of the sheets from an impression cylinder takes place within the aforementioned travel path of the end sections of the chain guides, there will then have been added to the aforementioned centrifugal forces, actuating forces which act upon roller levers of the gripper bars and by which sheet grippers borne by the gripper bars are normally opened counter to the action of spring forces. And, finally, the drive forces transmitted from the sprocket to the conveyor chain act within the aforementioned travel path in a manner which promotes wear, inasmuch as the teeth which are located, respectively, in the infeed region of the sprocket are loaded with the major part of the drive force acting on the part of the sprocket upon the conveyor chain.
It is accordingly an object of the invention to provide a conveyor chain for a gripper system-bearing chain conveyor of a printing press by which heretofore experienced wear of the chain conveyor is reduced.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a conveyor chain for a gripper system-bearing chain conveyor of a printing press, the conveyor chain having standard chain links and special chain links, both types of which are formed by link pins carrying chain rollers, and chain plates articulatedly connecting the link pins to one another, the special chain links serving to connect the conveyor chain to the gripper system, comprising two row-wise arranged chain-roller sections rotatable independently of one another, the chain-roller sections being disposed on the link pins of at least the special chain links.
In accordance with another feature of the invention, one of the chain-roller sections is engageable with a guide surface of a chain guide and is rollable thereon, and the other of the chain-roller sections is engageable in a sprocket and is at a standstill relative thereto.
In accordance with a further aspect of the invention, there is provided a sheet-processing printing press with a chain conveyor having gripper bars for transporting sheets, the gripper bars being borne by revolving conveyor chains when operating, each of the conveyor chains comprising standard chain links and special chain links, both types of which are formed by link pins carrying chain rollers, and chain plates articulatedly connecting the link pins to one another, the special chain links serving to connect the conveyor chain to the gripper system, and two row-wise arranged chain-roller sections rotatable independently of one another, the chain-roller sections being disposed on the link pins of at least the special chain links.
In accordance with a concomitant feature of the invention, one of the chain-roller sections is engageable with a guide surface of a chain guide and is rollable thereon, and the other of the chain-roller sections is engageable in a sprocket of the chain conveyor and is at a standstill relative thereto.
What is achieved thereby is that a first chain-roller section borne by a link pin remains capable of rolling in a turning region realized by a sprocket, while a second chain-roller section borne by the very same link pin remains at a standstill with respect to the sprocket due to the engagement by the second chain-roller section in the sprocket. With respect to the construction of the conveyor chain according to the invention, however, the occurrence of any sliding friction between a chain roller and a guide surface of a chain guide arranged in the region of the sprocket is thereby eliminated to the greatest possible extent. The drastic reduction, which can be achieved in the frictional forces between the conveyor chain and the abovementioned end sections of the chain guides is also accompanied by a corresponding reduction in the thermal loading of the chain conveyor that is equipped with this chain, whereas in the case of conventional chain conveyors in printing presses, at least in the case of heavily loaded chain rollers, thermal expansion of the latter can lead, in particular, to jamming thereof between an inner and an outer chain guide. Furthermore, the construction of the conveyor chain according to the invention counteracts the circumstance, which occurs in the case of conventional chain conveyors, that a chain roller exhibits different wear phenomena along the length thereof, resulting in increased surface pressures between the chain roller and a guide surface therefor on the chain guides.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a conveyor chain for a gripper system-bearing chain conveyor of a printing press, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: